After installing a smart coffeepot, motion-activated sensors, and even sensors that send alerts when drawers are left open, our reporter is left feeling like a stranger in her own home.

A few weeks after I gave my apartment a home-automation makeover, I found myself in a strictly 21st-century pickle: I was naked and shivering, stranded post-shower in my bathroom, trying to plot a route past a motion-activated camera to the freshly laundered towels I'd left by the bed. The camera was only meant to shoot pictures of trespassers, but the trigger that shuts off the system when I'm home is my smartphone—and I'd allowed the battery to run down. From technology's point of view, I was an intruder in my own apartment.

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In the end I gave up. The camera captured my awkward, dripping sprint, and I deleted the photos later. To avoid a repeat of the problem, I set up a key-chain fob—one with a nearly infinite battery life—to let the system know when I am home. It was one more step along my home-automation learning curve; as I was finding out, merging your digital and physical worlds requires some troubleshooting.

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Thing 1, Thing 2 Billion

The Internet has long since transformed the way we communicate and share information. We deposit checks from our phones, send messages through Snapchat, and carry around hundreds of books on our Kindles. But now the digital is creeping into our lives in a new way, letting us remotely monitor and control physical objects from thermostats to door locks to electrical outlets. The Internet of Things, which could eventually incorporate billions of objects, is starting to go mainstream.

Home-automation systems existed in the 1970s, but clunky remotes and steep prices limited their appeal—plus, the Internet didn't exist back then. More recently the rise of the smartphone has transformed the technology. It provided an ever-present and digitally connected new remote, allowing smart homes to get past the clap-on lights of bachelor pads of yore. Today's systems vary in complexity: You might prefer a simple setup (a single thermostat) or a more intricate one (a blanket system that controls all your lights, the sprinklers on your lawn, and the music in your living room).

I wanted to see if using technology to control my home would make my life easier or complicate things instead. Several players are competing in this market including Iris, Revolv, and Staples Connect; I chose SmartThings, an ecosystem known for being highly customizable. The starter kit costs $200 and comes with various "things"—a motion detector, sensors that attach to drawers, and two key-chain sensors. There's also a hub that grabs the information from all those components and beams it through the cloud to a mobile app.

First, I turned my phone into a presence tag, which is a GPS-automated ID that lets the SmartThings app establish a virtual perimeter around my place. When my cellphone moved into that geofenced zone my apartment knew I was home. SmartThings is open source, and a number of third-party companies offer products that can sync with the system. I connected a set of Sonos speakers to play music at predetermined times. I installed a camera to text me photos of trespassers, and then attached a sensor to the drawer where I keep my documents. I plugged my lamps and a coffeepot into smart outlets so they could turn on and off automatically. My Hue LED lightbulbs went online too: They now change colors with the flick of a finger on my smartphone.

Home, Never Alone

Home-automation devices can be controlled remotely, using a smartphone. Common gizmos might include: a coffeepot and its smart outlet trigger (A); Sonos music speakers (B); a sensor that alerts you when a drawer is open (C); a water-leak sensor (D).

My Life With Sensors

After all the sensors were up and running, I pressed Good Morning on the SmartThings app. "Good morning," my house replied. (So friendly!) "I changed your mode from Night to Home as you requested." All my lights went on, and my coffee began brewing. I sipped a cup while listening to the Beyoncé single I had asked SmartThings to play when I got out of bed. It felt like having an attentive yet invisible butler.

SmartThings wasn't built for amusement, though. The company's founder, Alex Hawkinson, conceived of the platform after a broken pipe had flooded his family's vacation house and led to a $100,000 repair bill. "My daughter was streaming Netflix," he recalls. "There was all this bandwidth in the air, but none of it was directed at the problem of what was going on in my home." Hawkinson has now installed about 200 smart devices in his home. And, yes, they include moisture sensors that can send text messages when water is detected.

The SmartThings blog is filled with stories of homes saved from fires, hurricanes, and leaky pipes. But the typical user is looking primarily for safety and security (surveillance cameras) and energy savings (turning off lights and appliances), along with a bit of convenience (morning coffee).

The settings can take some time to fine-tune. The day after I set up my system I had a friend over for dinner, but needed to dash out to buy butter. When in line I received a text from her: "All of your lights just went out!!!" I hadn't thought to program a scenario for guests when my phone and I aren't present. Hawkinson says he programmed his family's kitchen lights to turn on whenever the system detected motion, but then his wife walked down in her underwear and almost flashed the neighbors. He reprogrammed the lights to work only after 7 am.

The Walls Have Eyes

Embarrassing snafus simply take some experimentation to overcome. Privacy issues, on the otherhand, present a more enduring concern. Home-automation systems turn your physical behaviors into digital information—that's how they work. They can monitor when you get home from work, whether you're alone, and what time you go to bed.

Lee Tien, a senior staff attorney at the Electronic Frontier Foundation who specializes in privacy laws, worries that data-protection problems will multiply as the Internet of Things matures. "The home has traditionally been the most sensitive place that we recognize in both our legal system and in the social sense," he says. "All of these systems put a very large aperture inside that wall of privacy."

Last summer a hacker used a blackout command to successfully break in to a set of Hue bulbs. The consequences were hardly catastrophic—the lights shut off. But the possibilities are disturbing. One night I forgot to set my app to Good Night mode, which would have cut my security camera, before I went to sleep. I awoke to 17 texts: "There is motion in the Bedroom and photos have been taken at Alexis's Apartment." I scrolled through shots of myself in bed, sleeping.

SmartThings has strong privacy protections, encrypting data as it's captured by the hub and again as it's passed to the cloud. No one else had access to those photos, but the experience still felt creepy. If a hacker were to break in to my SmartThings app—or if someone got hold of my phone—he could track my movements in my home. And, Tien points out, even encrypted data can be obtained by a court order.

Right now, though, those concerns seem largely theoretical—and I've decided to keep the SmartThings system running. For one thing, my automated lights have cut my electricity bill by 10 percent. Of equal importance: The coffee is ready when I wake up, and so is Beyoncé.